Methods and system for partial cylinder deactivation

Abstract

Methods and systems are provided for reducing pumping losses during a partial deactivation. In one example, a method may include applying negative pressure to a deactivated cylinder group to remove gases trapped therein while an activated cylinder group continues to combust.

The invention claimed is: 
     
       1. An internal combustion engine, comprising:
 at least one cylinder head with at least two cylinders, in which each cylinder of the at least two cylinders has at least one inlet opening fluidly coupled to an intake line for supply of fresh air via an intake system, each cylinder has at least one outlet opening fluidly coupled to an exhaust line for discharge of exhaust gases via an exhaust-gas discharge system, a first cylinder group comprising a first cylinder of the at least two cylinders and a second cylinder group comprising at least a second cylinder of the at least two cylinders, wherein the first cylinder group is not deactivatable and the second cylinder group is deactivatable; 
 the intake system comprising a primary shut-off element configured to adjust fresh air flow to each of the first and second cylinder groups and a secondary shut-off element configured to adjust fresh air flow to only the second cylinder group, via which the supply of fresh air to the second cylinder group is selectively stopped; 
 a second cylinder group exhaust line is equipped with at least one exhaust shut-off element configured to adjust exhaust gas flow from the second cylinder group exhaust line to the exhaust-gas discharge system; and 
 a negative-pressure source is fluidly coupled to at least the second cylinder group exhaust line via a first negative-pressure line, wherein the first negative-pressure line is fluidly connected to the second cylinder group exhaust line at a position between the exhaust shut-off element and the second cylinder group. 
 
     
     
       2. The internal combustion engine of  claim 1 , wherein the primary shut-off element is arranged in the intake line, the intake line dividing downstream of the primary shut-off element to form a first cylinder group intake line and a second cylinder group intake line, and wherein the secondary shut-off element is arranged in the second cylinder group intake line. 
     
     
       3. The internal combustion engine of  claim 2 , wherein a second negative-pressure line fluidly couples the negative-pressure source to a portion of the second cylinder group intake line between the secondary shut-off element and the second cylinder group, and wherein the first negative-pressure line and the second negative-pressure line comprise first and second control valves, respectively. 
     
     
       4. The internal combustion engine of  claim 1 , further comprising a controller configured to:
 trap gases between the exhaust shut-off element and the secondary shut-off element in second cylinder group intake passages, exhaust passages, and cylinders when the second cylinder group is deactivated; and
 adjust the first and second control valves to more open positions in response to the second cylinder group being deactivated. 
 
 
     
     
       5. The internal combustion engine of  claim 1 , wherein the negative-pressure source comprises one or more of a vacuum pump, a negative-pressure region of the intake system, the first cylinder, a brake booster, and a vacuum-actuated valve. 
     
     
       6. A system, comprising:
 an engine comprising a first cylinder group having a first cylinder and a second cylinder group having a second cylinder, where only the second cylinder group is deactivatable; 
 a primary intake throttle arranged in a primary intake passage, the primary intake throttle shaped to adjust air flow to the first and second cylinder groups, and wherein the primary intake passage divides into a first cylinder group intake passage and a second cylinder group intake passage downstream of the primary intake throttle; 
 a secondary intake throttle arranged in the second cylinder group intake passage, the secondary intake throttle shaped to adjust air flow to only the second cylinder group; 
 an exhaust throttle arranged in a second cylinder group exhaust passage, the exhaust throttle shaped to only adjust exhaust flow out of the second cylinder group, and wherein a first cylinder group exhaust passage is fluidly coupled to the first cylinder group, wherein the first cylinder group exhaust passage merges with the second cylinder group exhaust passage downstream of the exhaust throttle; 
 a first vacuum source fluidly coupled to a portion of the second cylinder group exhaust passage between the exhaust throttle and the second cylinder group via a first vacuum line comprising a control valve; and 
 a controller configured to:
 adjust the control valve and apply negative pressure from the first vacuum source to the second cylinder group exhaust passage in response to the second cylinder group being deactivated. 
 
 
     
     
       7. The system of  claim 6 , wherein the controller is further configured to adjust the secondary intake throttle and the exhaust throttle to closed positions in response to the second cylinder group being deactivated. 
     
     
       8. The system of  claim 6 , further comprising a second vacuum line fluidly coupling a second vacuum source to a portion of the second cylinder group intake passage between the second cylinder group and the secondary intake throttle. 
     
     
       9. The system of  claim 8 , wherein the first vacuum source and the second vacuum source are different from each other and selected from the group consisting of a brake booster, an EGR valve, the primary intake throttle, and the first cylinder. 
     
     
       10. The system of  claim 9 , wherein the first vacuum source is the brake booster or the EGR valve and where the second vacuum source is the primary intake throttle or the first cylinder. 
     
     
       11. The system of  claim 6 , wherein exhaust gases from the first cylinder group mix with exhaust gases from the second cylinder group downstream of the exhaust throttle. 
     
     
       12. The system of  claim 6 , wherein the first cylinder group receives an amount of air flow greater than or equal to an amount of air flow received by the second cylinder group. 
     
     
       13. The system of  claim 6 , wherein the primary intake throttle generates vacuum as air flows around or through the primary intake throttle. 
     
     
       14. A method for control of an engine with a first cylinder group and a second cylinder group, comprising;
 deactivating only the second cylinder group of the engine, the second cylinder group having different cylinders than the first cylinder group; 
 closing intake and exhaust throttles configured to adjust gas flow to and from only the second cylinder group, respectively; and 
 removing gases trapped between the intake and exhaust throttles via a vacuum pump. 
 
     
     
       15. The method of  claim 14 , further comprising a primary intake passage housing a primary intake throttle shaped to adjust intake air flow to each of the first cylinder group and the second cylinder group, and where the primary intake passage divides downstream of the primary intake throttle to form a first cylinder group intake passage and a second cylinder group intake passage, and wherein intake air flows freely in the first cylinder group intake passage and intake air flow is adjusted via the primary intake throttle arranged in the second cylinder group intake passage. 
     
     
       16. The method of  claim 14 , wherein the first cylinder group comprises a first cylinder group exhaust passage fluidly separated from a second cylinder group exhaust passage of the second cylinder group, and wherein the exhaust throttle is arranged in the second cylinder group exhaust passage. 
     
     
       17. The method of  claim 16 , wherein the removing of gases further comprises adjusting a position of a first control valve in a first vacuum line fluidly coupling the vacuum pump to a portion of the second cylinder group exhaust passage between the second cylinder group and the exhaust throttle. 
     
     
       18. The method of  claim 17 , further comprising a second vacuum line comprising a second control valve, the second control valve adjusted independently of the first control valve. 
     
     
       19. The method of  claim 14 , wherein the first cylinder group and the second cylinder group comprise an equal number of cylinders. 
     
     
       20. The method of  claim 19 , wherein a vacuum source is one or more of a brake booster, an EGR valve, and the first cylinder.